1996 Volume 8 Issue 1 Pages 67-75
Mouse hind legs were exposed to single and multi-fractionated gamma rays with various time intervals between doses, and the ventral aspects of the legs were observed for ulceration from 2 to 8 months following irradiation. The doses necessary to produce ulcer (s) in 50% and 10% of the tested animals (UD 50 and UD 10, respectively) were calculated for each treatment schedule. Using these isoeffect doses, recovery curves and time-dose relationships of the target cells were assessed for ulceration. On the time interval-isoeffect dose curve, the isoeffect doses increased, decreased and increased again with increasing time intervals for two and four fractionation treatment schedules. The first peak was at 0.5 (or 0.5) day fractionation interval, and the trough at 4 (or 5) day intervals for 2 (or 4) fractions, when either the 10 or 50% ulceration was used as an end point. Applying the α/β model on UD 10 and UD 50, the flexured ose of the dose-response curve for the critical target cells for ulceration was calculated to be 0.23 Gy and 0.89 Gy, respectively.
